The present invention relates to prophylactic/therapeutic agents for atherosclerosis or xanthomatosis, more specifically, prophylactic/therapeutic agents for atherosclerosis or xanthomatosis containing a 2,6-di-t-butylphenol derivative as an active ingredient.
Oxidative denaturation of low-density lipoprotein (LDL) has been known as one of important causes of the development and progress of atherosclerosis and xanthomatosis (Steinberg, D., Parthasarathy, S., Carew, T. E., Khoo, J. C. and Witztum, J. L. Beyond Cholesterol; Modifications of low-density lipoprotein that increase its atherogenicity. N. Engl. J. Med. 320; 915-924, 1989). However, reports have shown that probucol which is an antioxidant has no therapeutic effect on atherosclerosis in clinical tests (Walldius, G., Erikson, U., Olsson, A., Bergstrand, L., Hadell, K., Johansson, J., Kaijser, L., Lassvik, C., Molgaard, J., Nilsson, S., Elinder, L. S., Stenport, G. and Holme, I. The effect of probucol on femoral atheroscleroses: the Probucol Quantitative Regression Swedish Trial (PQRST). Am. J. Cardiol. 84, 875-883, 1994).
As to therapy of arteriosclerosis, HMGCoA reductase inhibitor which is an antihyperlipidemic agent has so far been reported to inhibit the progress of arteriosclerosis (Scandinavian Simvastatin Survival Study Group Randomised trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study (4S). Lancet 344, 1383-1389, 1994). However, patients to be treated with the antihyperlipidemic agent are limited to hyperlipidemic patients, and the antihyperlipidemic agent is ineffective for arterosclerosis in the patients with familial hyperlipidemia. An antihyperlipidemic agent is considered to reduce the amount of LDL exposed to oxidative modification, thus showing an antiarteriosclerotic effect.
On the other hand, antioxidants capable of directly preventing oxidation of LDL are expected as prophylactic/therapeutic agents for atherosclerosis, but any drugs including the above-mentioned probucol have not been found to have a clinically sufficient effect as a prophylactic/therapeutic agent for atherosclerosis at present.
An object of the present invention is to provide a novel prophylactic/therapeutic agent for atherosclerosis having a clinically sufficient effect.
As a result of extensive research to solve the above problems, we found that compounds of general formula (1): 
wherein
R1 represents a hydrogen atom, an acyl group or an arylalkoxycarbonyl group,
R2 represents a lower alkyl group,
R3 represents a hydrogen atom or a lower alkyl group, and
R4, R5 and R6 may be identical or different and each represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group or an optionally substituted arylalkyl group, or
R2 and R4 together with the oxygen atom may form a furan or dihydrofuran ring, or
R5 and R6 may combine to form a cycloalkyl group or a heterosubstituted cycloalkyl group in which one or more methylene groups of the cycloalkyl group are replaced by oxygen, sulfur or alkyl-substituted nitrogen atoms, provided that R6 is absent when R2 and R4 together with the oxygen atom form a furan ring have a potent inhibitory effect against atherosclerosis in rabbit atherosclerosis models and murine atherosclerosis models as well as a potent inhibitory effect against xanthomas in murine xanthoma models.
Compounds of general formula (1) have been shown in JPA No. 6-206842/94. The publication contains the antioxidative data of the compounds demonstrating that they are useful as therapeutic agents for atherosclerosis, myocardial infarction and other diseases as well as that they are effective as antioxidants for ischemic organ disorders such as atherosclerosis, myocardial infarction, cerebral apoplexy, etc., but does not contain any test examples in which models are employed.
For the definition of R1 in general formula (1), the acyl group preferably contains 1 to 10 carbon atoms, the examples of which include acetyl, formyl, propionyl and benzoyl groups. The arylalkoxycarbonyl group preferably contains 7 to 11 carbon atoms, the examples of which include a benzyloxycarbonyl group.
R1 is preferably a hydrogen atom or an acyl group, more preferably a hydrogen atom. When R1 is an acyl group, it is preferably an acetyl group.
The lower alkyl group for R2 and R3 means a straight or branched alkyl group containing 1 to 6 carbon atoms, the examples of which include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl and t-butyl group.
R3 is preferably a hydrogen atom.
The alkyl group for R4, R5 and R6 means a straight or branched alkyl group preferably containing 1 to 20, more preferably 1 to 10 carbon atoms, the examples of which include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, pentyl, i-amyl, hexyl, heptyl, octyl, nonyl and decyl groups. The alkenyl group means a straight or branched alkenyl group preferably containing 2 to 20, more preferably 2 to 10 carbon atoms, the examples of which include vinyl, allyl, butenyl, pentenyl, geranyl and farnesyl groups. The alkynyl group means a straight or branched alkynyl group containing 2 to 20, preferably 2 to 10 carbon atoms, the examples of which include ethynyl, propynyl and butynyl groups. The aryl group preferably contains 6 to 20, more preferably 6 to 10 carbon atoms, the examples of which include phenyl, tolyl, xylyl, biphenyl, naphthyl, anthryl and phenanthryl groups. The arylalkyl group means an alkyl group having an aromatic hydrocarbon substituted for a hydrogen atom on the alkyl group, preferably containing 7 to 20, preferably 7 to 11 carbon atoms, the examples of which include benzyl and phenethyl groups.
The above-mentioned alkyl, alkenyl, alkynyl, aryl and arylalkyl groups may have one or more substituents selected from halogen atoms, lower alkyl, lower alkoxy, aryloxy containing 6 to 10 carbon atoms, hydroxy, amino, nitro and/or trifluoromethyl groups. Specifically, halogen atoms include chlorine, bromine, iodine and fluorine; lower alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl and t-butyl groups; alkoxy groups include methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, s-butoxy and t-butoxy groups; and aryloxy groups include phenoxy, 3,5-di-t-butyl-4-hydroxy-2-methylphenoxy and naphthoxy groups.
Preferably, R2 and R4 together with the oxygen atom may form a furan or dihydrofuran ring, which is fused with the benzene ring of general formula (1) to form a benzofuran or dihydrobenzofuran ring, respectively. More preferably, R2 and R4 together with the oxygen atom form a dihydrofuran ring, and R6 is absent when R2 and R4 together with the oxygen atom form a furan ring.
The cycloalkyl group formed by R5 and R6 is preferably a cycloalkyl group containing 3 to 8 carbon atoms, the examples of which include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl groups. The examples of the heterosubstituted cycloalkyl group in which one or more methylene groups of the cycloalkyl group are replaced by oxygen, sulfur or C1-6 alkyl-substituted nitrogen atoms includes, for example, tetrahydrothiopyranyl, N-methylpiperidyl and tetrahydropyranyl groups. A heterosubstistituted cycloalkyl group containing one or more oxygen atoms is preferred, and a tetrahydropyranyl group is especially preferred.
Especially preferred compounds of general formula (1) having the above-defined substituents are as follows:
4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxy-2-methyl-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxy-2,2-dimethyl-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-diethyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-di-n-propyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-di-n-butyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxy-2-octylbenzofuran;
4,6-di-t-butyl-5-hydroxy-2-octyl-2,3-dihydrobenzofuran;
2,4,6-tri-t-butyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-di-i-propyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-diphenyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-dibenzyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2-chloromethyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran-2-spiro-1xe2x80x2-cyclopentane;
4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran-2-spiro-1xe2x80x2-cyclohexane;
4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran-2-spiro-1xe2x80x2-cycloheptane;
4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran-2-spiro-1xe2x80x2-cyclooctane;
4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran-2-spiro-4xe2x80x2-tetrahydropyran;
5-hydroxy-4,6-di-t-butyl-2,2-dimethyl-7-propyl-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxybenzofuran;
4,6-di-t-butyl-5-hydroxy-2-methylbenzofuran;
2,4,6-tri-t-butyl-5-hydroxybenzofuran;
2,6-di-t-butyl-3-methyl-4-propyloxyphenol;
4-allyloxy-2,6-di-t-butyl-3-methylphenol;
1,3-bis(3,5-di-t-butyl-4-hydroxy-2-methylphenoxy)propane;
4,6-di-t-butyl-2,2-di-n-pentyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-di-n-octyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-di-n-heptyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-2,2-di-n-hexyl-5-hydroxy-2,3-dihydrobenzofuran;
2,2-di-i-amyl-4,6-di-t-butyl-5-hydroxy-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxy-2-methyl-2-(4,8,12-trimethyltrideca-3(E),7(E),11-trienyl)-2,3-dihydrobenzofuran;
4,6-di-t-butyl-5-hydroxy-2-methyl-2-(4xe2x80x2,8xe2x80x2,12xe2x80x2-trimethyltridecyl)-2,3-dihydrobenzofuran; and
4,6-di-t-butyl-5-hydroxy-2-(5-hydroxy-4-methyl-3(E)-pentenyl)-2-methyl-2,3-dihydrobenzofuran.
The compounds of general formula (1) used in the present invention can be synthesized according to the procedures described in JPA No. 6-206842/94, for example.
The prophylactic/therapeutic agents for atherosclerosis or xanthomatosis of the present invention can be used as various pharmaceutical compositions containing a compound of general formula (1) as an active ingredient in combination with a physiologically non-toxic solid or liquid pharmaceutical carrier. These pharmaceutical compositions are formulated and used in various dosage forms depending on the administration route to be used. Dosage forms include tablets, granules, pills, capsules, solutions, syrups, suspensions, emulsions and injections. Suitable pharmaceutical carriers include commonly used excipients, binders, disintegrants, lubricants, coating agents, dissolution-aids, emulsifiers, suspending agents, stabilizers and solvents.
The compounds of general formula (1) of the present invention and the pharmaceutical compositions described above can be administered orally or parenterally by such as intravenous injection, or as a sustained-release formulation, or topically by means of a catheter.
The actual dosage of the compounds of general formula (1) required for the prevention or treatment of atherosclerosis or xanthomatosis depends on the age of the patient, severity of condition, administration route or other factors, and an acceptable dosage which is effective is normally 1-1000 mg, preferably 100-300 mg per adult daily. Such dosage is preferably administered to the patient in need of the prevention or treatment in from one to three dose administrations daily.